Ignition system isolation circuit for internal combustion engines and the like



Dec. 31, 1968 A. w. LINDELI., JR

IGNITION SYSTEM ISOLATION CIRCUIT FOR INTERN COMBUSTION ENGINES AND THE LIKE Sheet Filed June 1, 1967 T UFISm ATTYS.

LATION CIRCUIT FOR INTERNAL COMBUSTION ENGINES AND THE LIKE IGNITION SYSTEM ISO SheefI Filed June 1, 1967 ATTYS.

Dec. 31, 1968 A. w. I INDELI., JR 3,418,990

IGNITION SYSTEM ISOLATION CIRCUIT FOR INTERNAL COMBUSTION ENGINES AND THE LIKE Filed June 1, 1967 sheet 3 F IGS.

/00 06 AL if. /J

I I T I I f /04 W U A Y /fz I To OTHER DETECTOR SWITCHES N4;

FIGA.

INVENTORZ BY ALBERT W. LINDELLJR.

ATTYS.

EGNITEON SYSTEM ISULATON CHRCUII FOR INTERNAL COMBUS'I'ION ENGNES AND THE UKE Albert W. Linde'ii, Jr., Columbus, Miss., assignor to American Bosch Arma Corporation, Columbus, Miss., a corporation of New York Filed .lune l, 1967, Ser. No. 642,952 11 Claims. (Ci. 1231-148) ABSTRACT F THE DISCLOSURE An ignition system isolation circuit for internal combustion engines employing means for generating pulses and at least two capacitive means charged by the pulses, the capacitive means being connected to engine fuel ignition mea-ns by switch means, which are actuated for permitting discharging of the capacitive means in synchronism with engine operation. The means for generating pulses for charging the two capacitive means is connected to control switches by diodes to isolate the two capacitive means from one another while connecting each capacitive means to common control switches. The control switches are actuatabie to complete a circuit to provide shut down of the engine when any control switch is closed, either manually or by detection of a malfunction in' engine operation. Capacity-'discharge ignition systems on different engines are connected together by a diode arrangement for providing simultaneous shut down through control switches upon a malfunction of any of the engines.

The present invention relates to an isolation circuit for capacity-discharge ignition systems suitable for use with internal combustion engines, and, more particularly, to an isolation circuit employed with safety control switches for connecting at least two capacitive means of capacitydischarge ignition systems together for shut down of engine operation upon actuation of a control switch.

In recent years, ignition systems have been developed which replcae the prior art breaker point apparatus and mechanical distributor with electronic circuitny for performing similar functions in response to electrical timing pulses produced in synchronism with engine operation. Many of these recent ignition systems employing electronic circuitry are referred to as high frequency systems since capacitive means is employed to store energy and discharge such energy quickly into windings of a step-up transformer to fire associated engine fuel ignition means. The quick discharge of energy from the capacitive means, providing high frequency operation, makes possible the use of transformers with fewer turns of conductors as compared to conventional transformers employed with conventional magneto ignition systems. One such high frequency ignition system is disclosed in U.S. Patent No. 3,311,783, entitled Ignition Apparatus for Internal Combustion Engines and the Like, issued Mar. 28, 1967, of Leslie E. Gibbs et al. and of common assignee herewith.

In ignition systems of the high frequency type with which the present invention is primarily concerned, these high frequency ignition systems have proved to be highly durable and reliable in use and are desirable to use for replacement of conventional magneto ignition systems on medium and large size internal combustion engines. These medium and large size engines often operate unattended, and if a malfunction occurs in either an engine or engine driven system, the malfunction should be detected immediately and the engine stopped promptly. One means of stopping engine operation is by stopping operation of its ignition system. In actual installations it is desirable nited States Patent to employ a number of malfunction detecting devices on each engine and to connect the systems of ydifferent engines into one control circuit arrangement so that, if one engine falters or malfunctions, all engines will be shut down. The detecting devices may include switches to sense, for example, engine vibration, temperature, oil pressure, and engine speed or excess current or voltage in the engine driven system.

'In the conventional magneto ignition systems the control switches for safety purposes have been of the single pole single throw type for use with a particular engine. When the capacity-discharge ignition systems, which may employ at least two capacitive means for discharging to provide the ignition spark, have been substituted for conventional magneto ignition systems or have been installed initially on medium and large size engine installations, a new control circuit arrangement is necessary to provide engine shut down. In accordance with the invention, it is ldesirable to provide an isolation circuit for the capacitydischarge ignition systems, employing two separate capacitive means, to connect the capacitive means to the control switches for stopping engine operation through the ignition systems. Also, installations employing more than one engine having capacityadischarge ignition systems, it is desirable to provide an isolation circuit connecting the capacity-discharge ignition systems to the Safety control switclies so that the safety control switches could be connected in a common safety circuit to monitor operations of the engines and effect shut down for all engines upon malfunction of any engine or engine driven system.

In accordance with the present invention, an ignition system isolation circuit is provided for an internal combustion engine and includes means for generating a series of pulses of alternating polarity, first capacitive means, and second capacitive means. There is employed first means, connected between the means for generating and the first capacitive means, which is selectively responsive to pulses of one polarity for charging the first capacitive means. Second means is provided, connected between the means for generating and the second capacitive means, which is selectively responsive to pulses of the other polarity for charging the second capacitive means. Also employed are a first and a second set of engine fuel ignition means, first switch means for connecting the first capacitive means to the first set of ignition means, and second switch means for connecting the second capacitive means to the second set of ignition means. Means is provided for actuating the first and second switch means to discharge the first and second capacitive means through the respective ignition means of the first set and second set in synchronism with engine operation.

Further, in accordance with the invention, control switch means is provided which is actuatable to complete circuit upon detecting a malfunction in operation of the engine. There is employed first unidirectional current flow means connecting the first means selectively responsive to pulses to the control switch means and second unidirectional current flow means connecting the se-cond means selectively responsive to pulses to the control switch means, whereby upon actuation of the control switch means to complete the circuit, the engine will be stopped. Preferably, the control switch means includes a detector switch actuatable upon detecting a malfunction in engine operation, such as, abnormal engine vibration, temperature, pressure or speed.

The ignition system isolation circuit of the present invention may be employed with capacity-discharge ignition systems on separate engines with each ignition system having its own means for charging its associated capacitive means. ln this arrangement, the ignition systems associated with the separate engines can be connected together a for monitoring the operation of the engines and providing shut down of all engines upon the ,malfunction of any engine.

For a better understanding of these and other features and advantages of the present invention, reference is made to the following drawings, in which:

FIG. 1 is a block diagram illustrating an overall ignition system and isolationcircuit in accordance with one form of the present invention;

FIG. 2 is a block diagram illustrating two overall ignition systems coupled together by an isolation circuit in accordance with the present invention and showing a connection for coupling still another ignition system to the isolation circuit;

FIG. 3 is a schematic diagram illustrating one form of the isolation circuit of FIG. 1; and

FIG. 4 is a schematic diagram illustrating one form of the isolation circuit of FIG. 2.

Referring now to the embodiment of the invention illustrated by way of example in FIG. l, there is shown an ignition system and isolation circuit, which provides engine shut down upon occurrence of predetermined conditions, in use in conjunction with an engine 16, which may be a conventional gasoline engine. The ignition system illustrated in FIG. 1 is characterized by a split bridge rectifier circuit especially adapted for use with engines having a large number of cylinders. For purposes of illustration, it will -be assumed that the engine has twelve cylinders and that the engine is of the usual fourcycle type. The proper tiring of the fuel in the engine cylinders is provided by engine fuel ignition means 12, which will ordinarily comprise circuitry including twelve spark plugs, one for each cylinder of engine 10 for igniting combustible fuel in the corresponding cylinder. The function of the remainder of the ignition system of FIG. 1 is to provide appropriate voltage pulses to the engine fuel ignition means in sequence so that each voltage pulse fires the proper spark plug at the proper time.

To accomplish proper timing, there is provided an alternating voltage generator 1d which is driven from engine crank shaft 16 by way of appropriate gearing 18, so as to produce at its output terminal 20 a train of pulses of alternating polarity in synchronism with rotation of crank shaft 16. The gearing 18 is such as to provide the desired integral multiple relationship between the frequency of rotation of crank shaft 16 and the frequency of recurrence of pulses at the output of generator 14, which may be provided by any suitable voltage generator.

The alternating opposite polarity voltage pulses from generator 14 are applied in parallel to a first rectifying means 22, and a second rectifying means 24, first rectifying means 22, for example, being responsive only to positive pulses from -generator 14 and second rectifying means 24 being responsive only to negative pulses to pass current therethrough. In the ignition system of FIG. 1, which is characterized by a split bridge rectifier circuit, the pulses from first rectifying means 22 are applied to rst capacitive means 26, lwhile the output of second rectifying means 24 is connected to second capacitive means 28. The first capacitive means 26 is electrically connected to first switch means 30 and the second capacitive means 28 is electrically connected to second switch means 32. In this example, iirst switch means 30 has six output connections 34, 36, 38, 46, `42 and `44, each of which is effective to produce capacity discharge from first capacitive means 26 through a particular one of the spark plugs in engine ignition -means 12, depending upon which of the input lines 46, 48, 50, 52, 54 and 56 from triggering pulse generator `58 is supplied with a trigger control pulse for triggering the discharge.

More specifically, input lines 46-56` conduct input trigger pulses to different ones of six silicon-controlled rectifiers, for example, in the first switch means to actuate a particular one of the silicon-controlled rectifiers to connect the first capacitive means 26 to fire on@ Q ih@ six spark plugs 75 connected to output lines 34-44, respectively. Therefore, to produce tiring of anyone of the six cylinders associated with the first set of engine ignition means 12, it is only necessary to apply trigger control pulse to the appropriate one of the trigger input lines 46-56 to render conductive the appropriate one of the silicon-controlled rectifiers in first s-witch means 30, thereby permitting current to iiow from the first capacitive means, a capacitor, to the appropriate spark plug.

Similarly, second switch means 32 has six output connections Gti-'70, each of which is effective to produce capacity discharge from second capacitive means 28 through a different particular one of the spark plugs in engine ignition means 12, depending upon which of the input lines 72482 from triggering pulse generator 58 is supplied with a control pulse for triggering the discharge of the particular silicon-controlled rectifier associated rwith a particular output connection. First switch means 30 and second switch means 32 are each effective to produce firing of a different set of six spark plugs in the engine ignition means by Way of their associated output connections to the ignition means. Accordingly, to produce firing of any one of the twelve cylinders of the ignition means 12, it is only necessary to apply a trigger control pulse to the appropriate corresponding one of the input lines to one of the first or second switch means.

The triggering pulse generator, in this example, may comprise a number of conductors equal to the number of cylinders in the engine, spaced from each other circumferentially around a center, and a magnet having a pole which is rotated about its center so as to induce pulses sequentially in the several conductors. The triggering pulse generator :may have its rotating element geared to crank shaft 16 by way of gearing 1S. The connections from the triggering pulse generator to the twelve input connections for the two switch means circuits are so arranged that the trigger control pulses are produced at the output leads of triggering pulse generator S8 on the proper lead for effecting the desired sequence of spark plug firing, this sequence being selected in appropriate fashion for the particular engine application according to principles well 'known in the art. The details of circuitry and construction of an overall ignition system which corresponds to the parts thus far desecribed in FIG. l are shown and described in the above-mentioned "U.S. patent of Gibbs et al.

An overall isolation circuit generally designated in FIG. 1 for safety monitoring and control of engine operation is electrically connected to the circuit of the ignition system. As previously stated, when capacity-discharge ignition systems have been substituted for conventional magneto ignition systems or have been installed initially on medium and large size engine installations, conventional safety control arrangements have not been readily connectable with the capacity-discharge ignition systems. The incompatibility of the capacity-discharge ignition system and the conventional safety devices is especially true in the type of capacity-discharge system described above having the split bridge rectifier arrangement for charging at least two capacitive means in the ignition system. In order to avoid having separate control switch arrangements and enlarging the control and safety monitoring arrangements, the isolation circuit for safety monitoring and control of the engine ignition system was developed.

In the present instance, isolation circuit 90 comprises first unidirectional current ow means 92 electrically connected to the output of `first rectifying means 22 and in parallel with iirst capacitive means 26. Isolation circuit 90 also includes second unidirectional current fiow means 94 connected to the output of second rectifying means 24 and in parallel :with second capacitive means 2S. The first and second unidirectional current flow means 92 and 94 have their outputs connected to control switch means 96, which preferably includes control and safety switches for stopping engine operation through shut down of the ignition system at a desired time or -upon detection of a malfunction in engine operation.

The detailed circuitry to provide a preferred isolation circuit operable with the split bridge rectifier type of capacity-discharge ignition system of FIG. 1 is shown in FIG. 3, illustrating one form of the isolation circuit 9i?. The isolation circuit of FIG. 3 comprises a diode 166, providing unidirectional current flow means, having its anode element connected to the output of first rectifying means 22 (not shown) and its cathode element connected to common junction 1ii2. A diode 1% provides another unidirectional current flow means having its anode element connected in the output. of second rectifying means 24 (not shown) and its cathode element connected to common junction 192. As shown in FIG. 3, there is also connected to common junction 192 a plurality of control switches. One control switch, which may be provided, for example, is manual kill switch connected between junction 192 and electrical ground. The ignition system will normally work in the manner previously described unless manual kill switch 196 is closed between junction 162 and ground to connect the first capacitive means through diode 190 and the second capacitive means through diode 194 to electrical ground, stopping engine operation.

A vibration switch 10S is shown connected between junction 102 and electrical ground to provide a safety monitoring device whch is actuated closed upon detection of excess vibration of the engine. Vibration switch 168 provides a safety monitoring device for detecting a particular malfunction of the engine and may be of a conventional type, such as manufactured by Frank W. Murphy Mfg., Inc. of Tulsa, Okla. If excess vibration of the engine occurs, vibration switch 16S will be actuated closed to connect the two capacitive means to electrical ground, stopping engine operation.

A plurality of other electrical leads 11i), 112 and 114 may connect other safety monitoring control and detector switches between junction 102 and electrical ground. For example, other detector switches which may be provided are temperature and pressure switches employed to ground out the ignition system should excess temperature or pressure actuate the respective switch closed, indicating a malfunction and stopping engine operation before the engine is damaged. Still other detector switches which may be employed are excess current or voltage switches in the electrical system of the engine or engine driven system for detecting malfunction in the operation of the engine installation to provide prompt shut down of the engine upon the occurrence of a malfunction detected by any of the control switches. rl`he isolation circuit with its control switch means provides an electrical path to facilitate grounding of both the first and second capacitive means through the isolation circuit so that the engine will be stopped upon any of the control switches detecting a malfunction or upon manual switch 106 being closed.

Referring to FIG. 2, there is illustrated two overall ignition systems -associated with separate engines and coupled together by an isolation circuit for safety monitoring and control of both engines in accordance with the present invention. Each of the ignition systems shown in FIG. 2 is similar to the one that is shown in FIG. l, except that only one capacitive means is employed in each ignition system. More specifically, there is represented in FIG. 2 a first engine 120 and, in this example, it will be assumed that the engine has six cylinders and is of the usual four-cycle type. The firing of fuel in the engine is provided by engine fuel ignition means 122 which comprises circuitry including six spark plugs, one for each cylinder of the engine for igniting fuel in the corresponding cylinder.

In the first engine ignition system there is provided an alternating voltage generator 124 which is driven from the first engine crank shaft 126 by way of gearing 128 to produce at the output of generator 124 a train of pulses of alternating polarity in synchronism with the rotation of crank shaft 126. The bearing provides the desired integral multiple relationship between the frequency of rotation of the crank shaft and the frequency of recurrence of pulses at the output of generator 124. The alternating opposite polarity pulses from generator 124 are supplied to first rectifying means 131i which passes only positive polarity pulses, for example. The pulses from first rectifying means 13u are applied to first capacitive means 132 to charge a capacitor therein. The capacitor in the first capacitive means is electrically connected to first switch means 134i which, in this example, has six output connections 13o-14d each of which is effective to connect the capacitive means to a particular one of the spark plugs in the engine ignition means 122 depending upon which of input lines 143-158 is supplied with a trigger control pulse for triggering the discharge of the capacitor.

In order to produce firing of any one of the six engine cylinders, it is only necessary to apply a trigger control pulse to the appropriate one of the input lines 148458 to render conductive the appropriate switch means circuit to permit current to iiow from the capacitor to the appropriate spark plug. The generation of the triggering pulses is produced by first triggering generator in sequence with engine operation through gearing 128 between the crank shaft 126 of the engine and generator 160. In this manner trigger pulses are produced by the first triggering pulse generator at a rate in sequence with first engine operation to actuate the first switch means to discharge the capacitive means to re the appropriate spark plug. The details of circuitry and construction of an overall ignition system in accordance with the block diagram described thus far in FIG. 2 is disclosed in detail in the above-mentioned US. patent of Gibbs et al.

1n accordance with employing the ignition system isolation circuit of the present invention with capacity-discharge ignition system on separate engines, there is also shown in FIG. 2 a second ignition system and second engine having parts similar to those of the first ignition system and engine and similar parts are identified by the same number designator with the addition of primes thereto. Since the operation of the second ignition system and engine is the same as the first ignition system and engine, operation of the second ignition system will not be described in detail.

Where two or more engines are employed in a system operating a driven system, such as used in power generating installations in which more than one engine drives the generating apparatus, an isolation circuit for safety monitoring of operation of the engines is desirable. The preferred isolation circuit for connecting the separate ignition systems together, while electrically isolating the systems from one another, is generally designated 17) in FIG. 2. The iso-lation circuit for monitoring and control of operation of the engines comprises first unidirectional current iiow means 172 connected to the output `of first rectifying means 130 and in parallel with first capacitive means 132. Isolation circuit 170 also includes second unidirectional current fiow means 176 connected to the output of second rectifying means 130 and in parallel with second capacitive means 132. The first and second unidirectional current flow means 172 and 176 have their outputs connected to control switch means 174.

Control switch means 174 preferably comprises a plurality of control switches, as described in regard to the control switch means of FIG. l, for safety monitoring and control of operation of the engines such that if a malfunction, for example, occurs in either engine system or the engine driven system, both engines will be stopped by grounding both capacitive means. Depending on the number of engines employed in the particular installation, other unidirectional current flow means similarly connected may be provided to connect capacitive means of another capacity-discharge ignition system to electrical ground through the control switch means. As shown in FIG. 2, third unidirectional current flow means 17S `may be employed to connect the capacitive means of another ignition system to the control switch means, for example. Through the isolation circuit 170 of FIG. 2, each ignition system is electrically isolated from the other ignition systems so that pulses produced by one ignition system for charging its capacitive means have no effect on the operation of the other ignition systems, but the ignition systems are connected together to be grounded through cornmon control switch means if a malfunction should occur in any engine system.

Referring to FIG. 4, there is shown a preferred embodiment of the isolation circuit which is preferably employed as isolation circuit 17tl of FIG. 2. The isolation circuit shown in FIG. 4 has parts similar to those Of the isolation circuit of FIG. 3. In the circuit of FIG. 4 there is provided a diode 180, providing a unidirectional current tlow means, which has its anode element connected to rst rectifying means 130 (not shown of FIG. 2 and its cathode element connected to common junction 182. The isolation circuit further includes a diode 184, providing a second unidirectional current tlow means, which has its anode element connected to the output of second rectifying means 130 (not shown) of FIG. 2 and its cathode element connected to common junction 182. Similarly, a diode 186 is provided for a third unidirectional current flow means to have its anode element connected to rectifying means of another ignition system employed with a third engine (not shown) and have its cathode element connected to junction 132, which provides a common junction for all engine ignition systems. In the present instance, the control switch means of FIG. 2 preferably comprises a plurality of detector switches which monitor, for example, engine temperature, pressure and vibration. A manual kill switch 138 is provided so that shut down of all engines at the same time may be facilitated if desired. Leads 190, 192 and 194 shown connected to the common junction 182 are provided for connection to the various detector safety switches preferably employed, in a manner similar to the connection for the safety detector switches described in regard to FIG. 3. By this arrangement, common control of all engine systems is provided, while isolating the ignition systems from one another so that damage to any engine or engine driven system is minimized by shut down of operation of all engine systems should a malfunction occur with any engine.

While the invention has been described with particular reference to specific embodiments of capacity-discharge ignition systems and employed with one or more engines, it will be observed that the isolation circuit may be employed in a variety of manners with one or more capacitydischarge ignition systems employed with one or more engines. For example, in installations employing large engines, the two rows of cylinders of the engine are spaced apart such that it may be desirable to employ two separate capacity-discharge ignition systems, one for each row of engine cylinders. The ignition system described in FIG. l, having two capacitive means for use with separate sets of engine ignition means, may be employed with such engines. However, in order to avoid wiring difficulties in connections from one alternating voltage generator and one triggering pulse generator, it may be advantageous to employ two separate complete ignition systems, as described in regard to FIG. 2, but employed on a single large engine. In this manner, eachv set of engine ignition means for each row of cylinders of the engine would have its own alternating voltage Igenerator operating to charge capacitive means for firing spark plugs. In this arrangement, the isolation circuit of FIG. 2 could be employed to electrically connect together each ignition system operating with the engine while isolating the operation of the ignition systems from one another to provide a common control connection.

It will be observed that the isolation circuit of the present invention for safety monitoring and control provides an advantageous arrangement for monitoring operation of the engine system and engine driven system. The isolation circuit enables a convenient and inexpensive manner of connecting together the capacity charging means for facilitating simultaneous shut down of operation of the ignition systems at a desired time or upon malfunction of an engine detected by the detector control switches. It will be appreciated by those skilled in the art that the isolation circuit in accordance with the invention provides a versatile arrangement that is useful with capacity-discharge ignition systems to eliminate more elaborate safety monitoring networks and duplication of safety monitoring equipment.

Other modifications of the ignition system isolatio circuit and its system described herein will occur to those skilled in the art. All such modifications are intended to be within the scope and spirit of the present invention as delined by the appended claims.

I claim:

1. In an ignition system isolation circuit for an internal combustion engine including means for generating a series of pulses of alternating polarity, first capacitive means, iirst means connected between the means for generating and the '.t'irst capacitive means and being selectively responsive to the pulses of one polarity for charging the rst capacitive means, second capacitive means, second means connected between the means for generating and the second capacitive means and being selectively responsive to the pulses of the other polarity for charging the second capacitive means, a first and a second set of engine fuel ignition means, rst switch means `for connecting the first capacitive means to the iirst set of ignition means, second switch means for connecting the second capacitive means to the second set of ignition means, and means for actuating the iirst and second switch means to discharge the first and second capacitive means through the respective ignition means of the tirst set and second set in synchronism with engine operation, the combination therewith of: control switch means actuatable to complete a circuit, rst unidirectional current ow means connecting the rst means selectively responsive to pulses to the control switch means, and second unidirectional current flow means connecting the second means selectively responsive to pulses to the control switch means, whereby upon actuation of the control switch means to complete the circuit, the engine will be stopped.

2. The ignition system isolation circuit of claim 1 in which the control switch means includes a detector switch actuatable upon detecting a malfunction in engine operation to complete the circuit.

3. The ignition system isolation circuit of claim 1 in which each unidirectional current flow means includes a diode.

4. The ignition system isolation circuit of claim 1 for use with a second internal combustion engine further comprising second engine capacitive means, second engine means for charging the second engine capacitive means, second engine fuel ignition means, second engine switch means for connecting the second engine capacitive means to the second engine ignition means, and second engine means for actuating the second engine switch means to connect the second engine capacitive means to the second engine ignition means for discharging the second engine capacitive means through the second engine ignition means in synchronism with second engine operation, and third unidirectional current tlow means for conecting the second engine means for charging to the control switch means, whereby when the control switch means is actuated to connect the lfirst means selectively responsive to pulses and the second means selectively responsive to pulses and the second engine means for charging in the circuit of the control switch means, operation of the rst and second engines will be stopped.

5. In an ignition system isolation circuit for an internal combustion engine including first capacitive means,

first means for charging the first capacitive means, a first and second set of engine fuel ignition means, rst switch means for connecting the first capacitive means to the first set of ignition means, lirst means for actuating the first switch means to connect the first capacitive means to the first ignition means for discharging the rst capacitive means through the first ignition means in Synchronism with engine operation, second capacitive means, second means for charging the second capacitive means, second switchrneans for connecting the second capacitive means to the second set of ignition means, and means for actuating the second switch means to connect the second capacitive means to the second ignition means for discharging the second capacitive means through the second ignition means in synchronism with engine operation, the combination therewith of: control switch means actuatable to complete a circuit, first unidirectional current flow means connecting the first means for charging the first capacitive means to the control switch means, and second unidirectional current flow means connecting the second means for charging the second capacitive means to the control switch means, whereby upon actuation of the control switch means to complete the circuit, operation of the engine will be stopped.

6. The ignition system isolation circuit of claim 5 in which each unidirectional current flow means includes a diode.

7. The ignition system isolation circuit of claim 5 in which the control switch means includes a detector switch for detecting a mulfunction in operation of the engine so that when a malfunction occurs the detector switch will be actuated to complete the circuit stopping operation of the engine.

8. In an ignition system isolation circuit for at least two internal combustion engines including first capacitive means, first means for charging the first capacitive means, first engine fuel ignition means for a first engine, -first switch means for connecting the first capacitive means to the first ignition means, means for actuating the first switch means to connect the first capacitive means to the first ignition means for discharging the first capacitive means through the first ignition means in synchronism with first engine operation, second capacitive means, second means for charging the second capacitive means, second engine fuel ignition means for a second engine, second switch means for connecting the second capacitive means to the second ignition means and means for actuating the second switch means to connect the second capacitive means to the second ignition means for discharging the second capacitive means through the second ignition means in synchronism with second engine operation, the combination therewith of: control switch means actuable to complete a circuit, first unidirectional current flow means connecting the first means for charging the first capacitive means to the control switch means, and second unidirectional current flow means connecting the second means for charging the second capacitive means to the control switch means, whereby upon actuation of the control switch means to complete the circuit, operation of the rst and second engines will be stopped.

9. The ignition system isolation circuit of claim 8 in which each unidirectional current flow means includes a diode.

10. The ignition system isolation circuit of claim 8 further including a manually actuable switch connected in parallel circuit with the control switch means between the first and second unidirectional current flow means and electrical ground so that upon closing of said manual switch the first and second engines will be stopped.

11. The ignition system isolation circuit of claim 8 in which the control switch means includes a detector switch for detecting a malfunction in operation of one of the engines so that when a malfunction occurs, the detector switch will be actuated to complete the circuit stopping operation of the engines.

References Cited UNITED STATES PATENTS 1,907,516 5/1933 DaVS 123-48 2,714,290 8/1955 Rachuig 60-97 3,356,896 12/1967 Shano 123-148 MARTIN P. SCHWADRON, Primary Examiner.

ROBERT R. BUNEVICH, Assistant Examiner. 

